Single and multiple fluid cartridge assemblies are generally known to dispense fluid materials, such as reactive adhesives, which typically contain two components that need to remain separated and applied quickly after mixing. An example of a single fluid cartridge assembly is disclosed in commonly owned international patent application No. PCT/US02/39041, filed on Dec. 6, 2002. Examples of multiple fluid cartridge assemblies are disclosed in, for example, U.S. Pat. Nos. 4,220,261, 4,961,250, and 5,310,091.
In U.S. Pat. No. 5,310,091, a dual fluid cartridge includes a front and a rear chamber formed by an outer cartridge and an inner cartridge, respectively. Piston seals are used to separate the fluids within the cartridges. Movement of the inner cartridge under the influence of a plunger causes the inner cartridge and upper piston to advance axially within the outer cartridge. The inner cartridge is in fluid communication with a piston tube, which extends through a front chamber up to a cartridge outlet. Movement of the inner cartridge within the outer cartridge causes the fluids in the inner cartridge and the outer cartridge to be dispensed. To fill the inner cartridge chamber and the outer cartridge chamber with the fluids, the fluids are forced into the cartridge outlet forcing the inner cartridge and the upper piston to retract axially within the outer cartridge.
During the process to fill the inner cartridge chamber and the outer cartridge chamber with fluid, a force is provided to the piston tube that can cause the piston tube to detach from the outer cartridge. Although the risk of detachment is generally low, the severity of the problem caused can be very high. In conventional systems, detecting whether the piston tube has detached from the outer cartridge is difficult, and may include, for example, an air pressure test or a destructive analysis. The air pressure test involves checking the pressure of air in the outer cartridge chamber and in the inner cartridge chamber for air pressure decay discretely, and then checking the two chambers for air pressure decay together. If both of the chambers exhibit large pressure decay discretely, and neither of the chambers exhibit large pressure decay together, it is an indication that the piston tube has detached from the cartridge assembly. However, the air pressure test can be time consuming and expensive, and requires the appropriate testing equipment. The destructive analysis involves disassembling or destroying the fluid cartridge, which can render the fluid cartridge non-operational.
Therefore, there is a need for an improved system and method for filling and dispensing fluids from a cartridge assembly, and for detecting whether the piston tube has detached from the outer cartridge